Lenses for digital cameras usually have zoom and/or focus systems operated by a rotary mechanism with a rubber ring on its outer peripheral surface. Depending on the type some lenses have two such rubber rings to allow operation of both zoom and focus functions while some lenses have only one. In the case of underwater photography it is necessary to be able to operate the zoom and/or focus functions of the camera, therefore the port which houses the lens must be equipped with a device which allows operation of these functions from a position external of the camera housing.
It is also important that the lens can be easily attached and detached from the lens coupling device of the lends port as removal of the camera and lens from the housing and port is frequently required, for example to change a battery or indeed to change the lens mounted on the camera.
Attempts have been made to meet these requirements by manufacturing a lens port which uses a gear system to transmit rotational force from outside the port to the lens positioned within the port. This type of construction requires the user to mount gear rings onto the outer periphery of the lens before the lens is inserted into the port. In some cases the rubber ring on the lens must be removed prior to mounting the gear ring on the lens. The gear ring must be precisely positioned on the lens so that when the lens is inserted into the port the gear ring on the lens and the gear or cog provided on the inside of the port mesh correctly.
In another construction the gear or cog drives a gear ring mounted on the inside of the port. The gear ring is provided with one or more, usually two, ribs which engage corresponding slots in a ring which the user mounts on the lens prior to insertion of the lens into the port. When inserting the lens into the port care is necessary to ensure the correct engagement between the ribs and slots.
Although the use of gears for torque transmission provides a reliable and efficient method care and attention is necessary when inserting the lens into the port otherwise the lens must be removed from the port and re-inserted. If the problem is not discovered until the camera is underwater the photographer must return to the surface or not use the zoom/focus functions.
U.S. Pat. No. 5,822,622 shows a further alternative in which a ring with a magnet attached is mounted on the lens and the port also has a rotatable ring with a magnet thereon. Rotation of the ring on the port causes the ring on the lens to also rotate. Insertion of the lens into the port is simplified as alignment is less critical but the diameter of the rotatable ring on the port is quite large and rotation of the ring by one hand is awkward.
United States Patent application 2006/0177206 shows yet another approach to solving this problem by providing rollers on the inside of the port which are mounted on a rotatable ring. The rollers engage the rubber ring on the lens to rotate the zoom/focus ring. However, again the large diameter of the external ring makes the construction difficult to operate particularly with one hand.